If you want to address the OP more specifically, it is also appropriate for the OP to explain why a basement apartment is not an option, where there might be disadvantages from their point of view, etc., then a discussion can actually start and not just generalized answers be given.
And this "carrying crates"... you only carry twice, once when buying into the basement apartment and then again when returning the empty bottles.
In the floor plan, I see terrace accesses from the dining/kitchen area, where the table is quite in the way. In post 15 shows how the house with a raised terrace could even fit.
In post 29 then the architect’s design (with a really somewhat convoluted kitchen layout so that a terrace door fits there. The terrace planning is only hinted at there. All indications are no more than 2 meters deep, not a great terrace spot if you want to eat, sit, grill there.
And from post 38 on there is also the discussion about the allowable wall height and the measurement of the reference point for it.
And when rereading I notice
We would have about 1.5m to the terrace according to our plan. Not compared to the 8 meters past desk, dining table, toys and couch that we have now
Yes, but the 1.5 m is only if you are standing straight at the counter in the kitchen planned by the architect. And then you don’t get onto the "usable part" of the terrace, but rather first onto the access to the usable part of the terrace.
And, since yesterday and post 64 we have been discussing the tone.
So now I have checked whether my initial claim about the OP is also correct. But apart from the "carrying" I have found nothing. And the carrying can really be put into perspective, e.g. post 65.